This invention relates to a leverage mechanism for amplifying a mechanical displacement produced by applying a voltage to a piezoelectric element which is employed as a driving element.
It is known to produce a mechanical displacement by applying a voltage to a piezoelectric element and amplify the displacement by a leverage mechanism. A displacement amplification device of this mechanism is shown, for example, in U.S. Pat. Nos. 4,675,568 and 4,874,980.
The known displacement amplification device is an assembly of a piezoelectric element, a displacement amplifying metal member and a resilient metal beam. The amplifying metal member has a central support part and a pair of lever arms which are arranged oppositely and symmetrically with respect to a center axis of the metal member. Each of the two lever arms is connected to the support part by a thin-walled hinge section which becomes the fulcrum of the lever action. The longitudinal axis of the piezoelectric element is oriented perpendicular to the center axis of the amplifying metal member, and the two opposite ends of the piezoelectric element are bonded to the root end sections of the two lever arms, respectively. The beam is made of a resilient metal sheet, and at its two opposite ends the beam is fixed to the tip ends of the two lever arms.
When a driving voltage is applied to the piezoelectric element in the above device a longitudinal displacement of each end of the piezoelectric element is transmitted to the adjacent lever arm, and the lever arm makes lever action to amplify the displacement at its tip end. Since the amplified displacement is transmitted to the resilient beam fixed to the tip ends of the two lever arms, the beam makes a buckling motion. As a consequence there occurs a change in the distance between the center of the beam and an end of the support part of the amplifying metal member. This change in distance is a maximal displacement of the beam and is used as the output of the displacement amplification device.
It will be apparent that the above described displacement amplification device provides only one output. Therefore, if two simultaneous outputs are required it is necessary to use a parallel combination of two units of amplification mechanisms. Further, if it is required that the two outputs should be different in magnitude it is necessary to differently design the two units of amplification mechanism to be used in combination. Although two simultaneous outputs can be obtained by combining two units of amplification mechanisms the combined mechanisms inevitably become large in size, and the combination of the two sets of mechanisms entails a considerable rise in cost.